Diesel fuel, particularly No. 2 fuel oil, has the tendency to jell or "wax" in cold weather. This jelling of diesel fuel is a particularly acute problem in the trucking industry during the winter months in the northern portion of the United States and throughout Canada. During the winter months, temperatures and wind chill factors frequently reach minus 30.degree. F. in these areas. In such a temperature and wind chill range, diesel fuel tends to jell or wax both in the fuel tank itself and within the fuel line leading from the tank to the engine. In the severest incidence of jelling, the diesel engine completely fails. The truck thus must be towed to a service area and the fuel tank heated. The towing and down time of the truck results in increased transportation costs. In less severe instances, the jelling can result in loss of power so that the trucks are forced to travel at a slow rate of speed. This also results in increased transportation costs.
Numerous methods and apparatus have been used in the past in an attempt to solve this problem. A heating mechanism interposed in the fuel supply line from the fuel tank to the engine is one of the more frequently used mechanisms. U.S. Pat. No. 3,929,187 issued to Edwin E. Hurner illustrates such a mechanism. The device disclosed in the Hurner patent utilizes the heated water or coolant from the engine to supply heat to a heat exchanger through which a fuel line passes. Another prior art mechanism consists of a fuel filter which also serves as a heat exchanger to heat the fuel passing therethrough. Both of the above heat exchangers are relatively complex and, hence, expensive structures to produce. Also, since these heat exchange devices are disposed within the path of the fuel line and not within the fuel tank itself, they do not prevent the jelling or "waxing" of the diesel fuel within the fuel tank.
The mixing of different types of fuel, as well as the use of additives to the fuel have also been attempted in an effort to prevent the jelling of diesel fuel at low temperatures. The use of additives requires that the additives be added at appropriate times and in appropriate amounts. Also, the additives tend to cause additional wear on the diesel engines.
Another method utilized in the prior art to prevent the jelling of the fuel within a diesel fuel tank was by passing a portion of the exhaust pipe through the gas tank. However, this method does not provide the capability of heating the fuel prior to starting the engine.